On the Developer Tutorials blog, Akash Mehta has posted an introduction to working with command-line PHP scripts and cron jobs for site automation.

Scheduled tasks are a fairly common feature in modern web applications. From cleaning out caches every 24 hours to checking subscription periods and even generating reports, more web applications live by the clock than ever before. But how do we schedule the execution of a PHP script on the server side?

He shows the two key things to getting it working - an example of a command-line call to a PHP script (executed through his /usr/bin/php) and an example of a line from a crontab showing how to execute the script at midnight every day.

On the PhPL33t blog, there's a guide for automating the creation of email addresses with the Plesk administration application:

In 2003 I wrote "Plesk Auto Email", the first fully funtional Plesk email automation suite. Now, I am going to show you how to do it. You will need a dedicated server with Linux, Plesk 7.5 and higher, php5, mysql5, and root access. This will show you how to code the auto creation, I am not going into deletions and edits at this time because I don't have all night to blog.

Included are the database table to store the commands in, the PHP script to create the commands (the integration into the other piece of software) and the PHP cron script that looks in the command table and executes each as it goes through.

Richard Heyes has shared an epiphany he's come up with - a method for running scripts in a web-based environment using lynx.

OK maybe not to you, but it has just occurred to me, and things don't come to me all that fast these days. Cron jobs. [...] You can have a directory inside your webroot called "cron" (imaginative eh?) with scripts in there that are run via cron.

His method uses the cron daemon on the machine to invoke lynx and call the web page through its url. Of course, there are advantages and disadvantages of the method (including having the script open to the world - scary). Be sure to check out the comments for other suggestions from fellow developers.

Both this post on the Zend Developer Zone and tis post on the International PHP Magazine's website point to a new article over on the IBM developerWorks website by Jack Herrington, Batch processing with PHP.

What do you do when you have a feature in your Web application that takes longer than a second or two to finish? You need some type of offline processing solution. Check out several methods for offline servicing of long-running jobs in your PHP application.

He talks about cron and its role in offline processing (including a basic primer on its format) before getting into the example itself. He looks at three examples:

• building an email queue
• building a generic queue system
• dumping out the database

Each example comes complete with code and descriptions to help you work them up on you very own system.